# Power-Sharing Index: Measure Construction & Validation

**Author:** Jessala A. Grijalva, PhD
Postdoctoral Fellow, Institute for Latino Studies, University of Notre Dame

## Overview

This repository contains the construction and validation pipeline for the **Power-Sharing Index (PSI)**, a measure of *de facto* power distribution across social groups in democratic systems. PSI captures whether political power can transfer across demographic boundaries — the dimension that standard democracy indices miss.

**Target journal:** *Political Analysis*
**Status:** Working paper (V-Dem Working Paper series)

## The Problem

Standard democracy indices show moderate-to-high scores during periods of massive group-level exclusion. V-Dem's Electoral Democracy Index averaged 0.35 during the Herrenvolk era (1789–1865), when African Americans were enslaved, women could not vote, Indigenous peoples were not citizens, and citizenship was restricted to "free white persons." PSI addresses this by measuring cross-group power-sharing rather than procedural quality.

## Data Source

**Varieties of Democracy (V-Dem) v15**
https://v-dem.net/data/dataset-archive/

The raw V-Dem data file (`V-Dem-CY-Full+Others-v15.rds`) is not included due to size. Download it from V-Dem and place it in `data/raw/`.

## File Structure

```
psi-scale/
├── Phase_1_PSI_Construction.qmd   # Builds PSI, compares aggregation methods, sensitivity analysis
├── Phase_2_PSI_Validation.qmd     # Psychometrics: α, PCA, convergent/discriminant validity
├── Appendix.qmd                   # Publication-ready appendix (loads precomputed results)
├── R/
│   └── 00_setup.R                 # Shared setup: packages, constants, helper functions
├── data/
│   ├── raw/                       # V-Dem source data (not tracked — download from v-dem.net)
│   └── processed/
│       ├── psi_phase1_results.rda # Constructed PSI (generated by Phase 1)
│       └── psi_phase2_results.rda # Validation results (generated by Phase 2)
├── scratch/                       # Not tracked — exploratory work, reference papers
├── psi-scale.Rproj
├── .gitignore
├── LICENSE
└── README.md
```

## Reproduction Instructions

### Quick Start (from processed data)

If `data/processed/psi_phase1_results.rda` and `psi_phase2_results.rda` are present, the Appendix renders in seconds without the raw V-Dem data:

```r
quarto::quarto_render("Appendix.qmd")
```

### Full Pipeline (from raw data)

```r
# 1. Open psi-scale.Rproj in RStudio
# 2. Render Phase 1 first (constructs PSI, saves results):
quarto::quarto_render("Phase_1_PSI_Construction.qmd")
# 3. Render Phase 2 (loads Phase 1 results, runs validation):
quarto::quarto_render("Phase_2_PSI_Validation.qmd")
# 4. Render Appendix (loads all precomputed results):
quarto::quarto_render("Appendix.qmd")
```

**Note:** Phase 1 must be rendered first — it saves the constructed PSI to `data/processed/psi_phase1_results.rda`, which Phase 2 and the Appendix load.

## PSI Specification (5 Indicators)

| Component | V-Dem Variable | What It Captures |
|-----------|---------------|------------------|
| Social Group Power | v2pepwrsoc | Power distributed across racial/ethnic/religious groups |
| Gender Power | v2pepwrgen | Power distributed between men and women |
| Civil Liberties Equality | v2clsocgrp | Equal civil liberties across social groups |
| Freedom from Torture | v2cltort | Freedom from state coercion against groups |
| Freedom from Killings | v2clkill | Freedom from political violence for control |

**Aggregation:** Hybrid method (geometric mean of 5 normalized components, multiplied by normalized Polyarchy score). See Phase 1 for rationale and sensitivity analysis.

## Related Repositories

- [`psi-apd`](https://github.com/jagrijalva/psi-apd) — American Political Development application (uses PSI to analyze US democratic trajectory)
- [`psiR`](https://github.com/jagrijalva/psiR) — R package for computing PSI (in development)

## Software

All analyses conducted in R using Quarto. Key packages: `tidyverse`, `psych`, `gt`, `ggcorrplot`, `scales`. See `sessionInfo()` output in each rendered document for exact versions.

## License

Code: MIT License. Data and documentation: CC-BY 4.0. See [LICENSE](LICENSE) for details.

The raw V-Dem data is subject to its own terms of use via the V-Dem Institute.
